Thread Black (or brown/olive to match) 70 denier / 8/0 (Semperfli Nano Silk 30D for small sizes)
Materials
Body Tying thread, built up thin and segmented (over the shank)
Rib Fine wire or fine tinsel (optional) (1 length)
Flash Pearl/opal Krystal Flash or tinsel (1-2 strands under the wing)
Wing/post Thin closed-cell foam (white or grey) (small strip)
How to tie it
Start thread behind the eye on the curved hook and wind a smooth, thin, slightly tapered segmented body back to the bend and forward again to the thorax area.
If ribbing, counter-wind a fine wire for segmentation and tie off.
Tie in a single strand or two of pearl flash pointing forward, to be pulled back under the wing later (it imitates the metallic air-bubble of an emerging midge).
Tie in a short strip of thin foam over the thorax as the wing/wingcase; the foam gives buoyancy so the fly sits high in the film when submerged.
Pull the flash back under the foam wing, secure, build a small thread head, whip finish and add a tiny drop of cement.